JPS6038818B2 - Color cathode ray tube landing characteristic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for measuring electron beam landing characteristics of a color picture tube.

When designing color picture tubes (hereinafter referred to as CPTs) and deflection hawks, it is important to accurately determine how much the center of the electron beam deviates from the center of the crab light dot, which is called the amount of landing error. need to ask. subordinate,
One way to determine this amount of deviation is to visually observe it using a microscope that has a magnification of 6 pitches or 8, and has a built-in scale with a minimum scale of about 2 inches. FIG. 1 shows an enlarged view of the landing state of an electron beam on the surface of a color cathode ray tube.

In the figure, 1 is the electron beam, 2 is red (R), green (G)
Or blue (B) crab light body, 3 is black stripe, 4
is the shadow of the shadow mask.

When measuring the landing state of the crab light surface as shown in FIG. 1, the outer shape of the electron beam is unknown due to the presence of the black strap 3, so it is determined based on the shape of the shadow 4 of the shadow mask.

However, since the shadow 4 of the shadow mask is not clear, it is difficult to determine the center of the electron beam 1 from the state of the shadow 4. Furthermore, since the boundary between the crab phosphor 2 and the black stripe 3 is not uniform, it is also not easy to find the center of the honey phosphor 2. Conventional methods for measuring landing characteristics have been based on visual inspection, which tends to cause variations in the measured values, and has drawbacks such as requiring training and taking a long time to measure accurately.

In addition, as a conventional device which solves the above-mentioned drawbacks, there is also a device as disclosed in Tokukan Sho 50-121633. This method focuses on the fact that the characteristic curve of optical output becomes symmetrical when the electron beam on the tube surface is placed in a symmetrical position, and by giving a periodic symmetrical deviation to the electron beam, the symmetrical response by the electron beam is calculated. The light emitting points are deviated by an equal amount, a point where their corresponding outputs are equal is detected, and the amount of deviation is taken as the amount of deviation in lasoding. That is, the above conventional method was performed on the premise that the optical output characteristic curve is symmetrical. However, the beam landing characteristics are affected by the symmetry and shape of the electron beam, and the shape of the electron beam is also greatly affected by the Hawker lens included in the electron gun. C for a given beam shape
The problem is that the PT must be selected and the adjustment state of the CPT focus lens must be constantly managed during measurement, making the measurement extremely complicated and almost impossible in practice. This invention was made in view of this point, and by detecting the state in which the amount of light emitted from the ant light surface reaches its maximum during optimal landing using a light fog conversion element, it is possible to easily manage the landing characteristics of the electron beam. It is an object of the present invention to provide a landing characteristic measuring device that does not require any of the following methods and can perform measurements simply, at high speed, and with high accuracy. FIG. 2 shows a diagram of the principle of this invention.

A state of good color purity is a state in which the electron beam 1 is most efficiently emitting light from the phosphor 2, and the center of the electron beam 1 and the center of the phosphor 2 coincide with each other, as shown by the solid line in FIG. It is in a state of being

In this state, if a magnetic field is applied to the electron beam from the outside and the electron beam is displaced from side to side as shown by the broken line in FIG. la and lb are in a state where adjacent crab light bodies are made to emit light. In this way, the electron beam 1 is displaced left and right by an external magnetic field, and the amount of light emitted from the crab light surface is controlled by the optical filter (second
When light is received by a photoelectric conversion element through a green filter (in the case of the figure), the strength of the external magnetic field 1 and the output B of the photoelectric conversion element become as shown in FIG. Figure 2b shows crab light body 2 and electron beam 1.
Since the output curve is for the case where the centers of If the center of beam 1 is shifted by 4×, then external magnetic field 1 is i
When , the output B of the photoelectric-optical conversion element is at its maximum, and the amount of external magnetic field i becomes the amount of landing deviation. Therefore, the displacement of the electron beam with respect to the intensity of the magnetic field is determined in advance, and the amount of deviation of the landing of the electron beam with respect to the crab light body is determined from the intensity of the magnetic field at the point where the optical force obtained from the photoelectric conversion element is maximum. For convenience of explanation, Figures 2 and 3 show the case where an external magnetic field is applied to the electron beam passing through one shadow mask hole, and the solid line indicates the position of the electron beam 1 when the external magnetic field is 0. The broken lines indicate the positions of the electron beams la and lb when an external magnetic field is applied. FIG. 4 shows a block diagram of an example of the present invention.

In the figure, 5 is a color cathode ray tube, 6 is an optical filter that passes only a specific color of light from the color cathode ray tube 5, and 7 is a photoelectric conversion element that converts the output of the optical filter 6 into an electrical signal. , 8 is an input circuit that temporarily holds the output of the photoelectric conversion element 7, 9 is a control circuit that stores the output of the photoelectric conversion element 7 from the input circuit 8, 10G or an external magnetic field generating coil for sub-deflection, 11 12 is a drive circuit that drives the external magnetic field generating coil 10 using the external magnetic field signal 1 from the control circuit 9; 12 is a television circuit that controls the screen of the color cathode ray tube 5 using the color signal and raster signal V from the control circuit 9; Reference numeral 13 denotes a display device for displaying the measurement results of the beam landing characteristics by the control circuit 9. The control circuit 9 serves as a monochromatic light emitting means that applies a color signal and a raster signal V to the television circuit 12 that drives the color cathode ray tube 5 to cause the tube surface of the color cathode ray tube 5 to emit light in a single color of red, green, or blue. operating and external magnetic field signal 1
In addition to the drive circuit 11, it also drives the external magnetic field generating coil 10 for sub-deflection, and also operates as a sub-deflection means to give an arbitrary amount of displacement to the electron beam.Furthermore, it switches the luminescent color of the tube surface and changes the direction of the electron beam. Photoelectric conversion element 7 when switching the amount of displacement
It also operates as a calculating means for measuring the landing characteristics by comparing with the output B of the. Next, the operation will be explained.

Using the color signal and raster signal V from the control circuit 9, the television circuit 12 makes the screen of the color cathode ray tube 5 monochromatic. The optical filter 6 passes only the color of the screen selected by the above operation. For example, if the tube surface is monochromatic green, only the green color is allowed to pass through. In this state, the photoelectric conversion element 7
The output from the control circuit 9 is sent to the control circuit 9 via the input circuit 8.
be memorized as . The external magnetic field signal 1 to the drive circuit 11 at this time is also stored in the control circuit 9. By changing the external magnetic field signal 1 from time to time and repeating the above operation, the control circuit 9 compares and calculates each optical output B, thereby obtaining the external magnetic field signal 1 at the peak value in the curves shown in FIGS. 2b and 3b. demand.
By multiplying the obtained external magnetic field signal 1 by the current coefficient obtained from the movement of the beam and displaying it on the display 13, the landing state of the position where the photoelectric conversion element 7 and the optical filter 6 are attached can be seen at a glance. Next, at the same time the color signal is switched from the control circuit 9 to the television circuit 12, the optical filter 6
If the same measurement is performed by switching between the two colors, the landing state of each of the three colors can be determined. Although it is possible to mechanically switch the optical filter 6, it is also possible to install red, green, and blue optical filters and a photoelectric conversion element in pairs, and then switch the output of the photoelectric conversion element 7 to perform measurement. can be done quickly. In addition, the input circuit 8 is a circuit that temporarily holds the output from the photoelectric conversion element 7, but in the case of a raster scanning system like a television screen, the output of the photoelectric conversion element 7 for a unit surface fin is as shown in Fig. 5. Therefore, it is necessary for the input circuit 8 to hold the output at a specific point in FIG.

The output circuit, sample hold circuit, and peak hold circuit can all be roughly combined with the A/D converter to form the input circuit 8. Note that in FIG. 5, the distance between each peak of the waveform corresponds to the horizontal scanning time (about 63.5 rsec). In the above-described practical example, the external magnetic field generating coil 10 is installed at the neck portion of the color cathode ray tube 5, but it may be installed at the front surface of the tube. Further, in the above-described practical example, only the measurement of the landing state was explained, but it can also be used as a color purity adjusting device by attaching it at several locations on the tube surface.

As described above, according to the landing characteristic measuring device for a color cathode ray tube according to the present invention, an electron beam is given a minute displacement by an external magnetic field, the change in the optical output is compared through an optical filter, and the external magnetic field at the peak of the output is compared. Since the landing state is detected from the intensity, it is possible to measure the landing state at a desired position on the tube surface of the color cathode ray tube by moving the detection section composed of an optical filter and a photoelectric conversion element. Therefore, the landing characteristics of color cathode ray tubes can be easily measured at high speed and with high accuracy, and it is also very effective when used for inspection and adjustment of color cathode ray tubes.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the landing state of an electron beam on the tube surface of a color cathode ray tube, Figures 2 and 3 are for explaining the principle of this invention, and Figures 2a and 3a are Figures 2b and 3b are partially enlarged views of the tube surface showing the state in which the electron beam is displaced by the magnetic field, respectively.
Figures a and 3a are characteristic diagrams showing the relationship between the magnetic field and the output of the photoelectric conversion element when the electron beam is moved, and Figure 4 is the Kazumi color cathode ray tube landing characteristic measuring device according to the present invention. FIG. 5, a block diagram of the anchor example, is a diagram showing the output waveform obtained by the photoelectric conversion element. 1...Electron beam, 5...Color cathode ray tube,
6... Optical filter, 7... Photoelectric conversion element, 9... Control circuit that also serves as monochromatic light emitting means and calculation means, 10... External as sub-deflection means. Magnetic field generating coil, 12... Television circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 5 Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. Monochromatic light emitting means for causing the entire tube surface of a color cathode ray tube to emit monochrome light via a television circuit, and auxiliary displacement means for displacing the electron beam on the tube surface by applying an external magnetism;
an optical filter that is installed opposite to the tube surface and allows only monochromatic light to pass; a photoelectric conversion element that outputs an electrical signal according to the output light of the optical filter; and an external magnetic field applied to the electron beam by the sub-polarization means. A color cathode ray tube characterized in that the color cathode ray tube is equipped with a calculation means for comparing and calculating the output of the photoelectric conversion element for various values, detecting the intensity of the external magnetic field at which the output becomes maximum, and measuring the landing state of the electron beam. Landing characteristics measuring device. 2. The landing characteristic measuring device for a color cathode ray tube according to claim 1, wherein the sub-biasing means is installed at a neck of the color cathode ray tube. 3. The landing characteristic measuring device for a color cathode ray tube according to claim 1, wherein the sub-biasing means is installed on a tube surface of the color cathode ray tube.